The formulation of modern detergent compositions, especially granular laundering compositions, has involved the use of a variety of materials, including sophisticated surfactants, enzymes, bleaches, fabric softeners, pH control agents, and the like. Typically, such compositions contain a builder material which serves a variety of functions, including water hardness sequestration, soil peptization, pH control, and the like. For many years, sodium tripolyphosphate was the builder of choice and, by itself, performed the aforesaid functions quite admirably. However, in recent years sodium tripolyphosphate has been removed from many detergent compositions. Currently, many fully-formulated detergent compositions contain a zeolite builder, a polycarboxylate builder, or mixtures thereof.
The development of high performance laundry and automatic dishwashing detergent compositions without phosphates has been a considerable challenge to the industry. From the performance standpoint, even the best sequestering builders may not optimally peptize soils or otherwise act as a dispersing agent and antiredeposition agent for soil that has been removed from fabrics. As can be imagined, in the modern automatic washing machine suboptimal performance will occur if solid soil that has been removed from the fabrics by the surfactant process were to redeposit onto the fabrics. In the dishwasher context, lime scale deposition on dishes and glassware remains problematic.
These shortcomings in phosphate-free granular detergents are well-known to formulators. Various dispersing and antiredeposition agents have been introduced into nonphosphate detergent compositions in order to enhance their performance. Typically, such materials have been prepared from synthetic polycarboxylate polymers, for example, polymers comprising acrylate, maleate or methacrylate moieties. While such synthetic polymers perform their intended use, they do have some drawbacks. For example, formulators of modern nonphosphate granular laundry detergents and, in particular, granular automatic dishwashing detergents, would prefer to use dispersing agents at levels up to about 12%, or greater, in products. However, this is difficult with polyacrylates since they are mainly based on petrochemical feedstocks rather than renewable resources. And, some petrochemical-based dispersants may not be sufficiently biodegradable to meet modern standards.
In light of the foregoing, there has been a continuing search for new dispersing agents for use in laundry detergents, automatic dishwashing detergents, and the like. The present invention employs natural starch which has been oxidized in the manner described hereinafter to achieve these desirable benefits.